Can I do oversampling by copying the same image multiple times? Will it effect my neural network accuracy?
This would be a pretty fun opportunity to experiment a bit. I know there's been breakthroughs in OCR technology by training the network on images that have been altered.

Long story short, there was a pre-process that took the source images and did minor manipulations to them. This involved skewing, rotating, changing resolution &amp; adding artifacts into the image to introduce "Noise". This allowed the network to learn to recognize characters more accurately. It may be worthwhile to create an image pre-processing pipeline that will do a variation of modifications to the source images. When training you may want to lower your learning rate &amp; split up your data into 70% train &amp; 30% test. Then you can loop through all the images repeatedly until you hit a maximum for the learning rate.

Some examples
https://matthewearl.github.io/2016/05/06/cnn-anpr/
https://medium.com/@shreyas.s/image-data-generation-for-optical-character-recognition-ocr-9b19300649c8